Iliamna lies in the transitional climate zone, characterized by an average annual precipitation of about 30 inches, and average annual temperatures of about 27 °F. The coldest month in 2013 was March, with a mean minimum temperature of 15.3 °F. The warmest month was July, with a mean maximum temperature of 66.9 °F.

Prior to 1935, "Old Iliamna" was located near the mouth of the Iliamna River, a traditional Athabascan village. A post office was established there in 1901. Around 1935, villagers moved to the present location, approximately 40 miles from the old site. The post office followed. Iliamna's current size and character can be attributed to the development of fishing and hunting lodges. The first lodge opened in the 1930s. A second lodge was built in the 1950s. During the 1970s and 80s, lots were made available by the Baptist church, and additional lodges were constructed.

Culture

In recent years, Iliamna has become a recreational and tourist attraction due to the excellent fishing at Iliamna Lake. The population is mixed, with non-Natives, Tanaina Athabascans, and Alutiiq and Yup'ik Eskimos.

Travel in Iliamna is usually by small plane, and seasonally by boat, four-wheeler, or snowmobile. Individuals also use personal vehicles, ATVs, and skiffs. Barges deliver bulk goods to the area via the Kvichak River. An improvised barge landing area is currently available at Iliamna. A breakwater, boat harbor, and dock are also available, although the dock is in poor condition. A state-owned airport with two gravel airstrips is located several miles west of Iliamna. Iliamna Air Taxi, Inc. provides scheduled mail, freight, and passenger air service to several Iliamna Lake communities. In addition to the state-owned airport, a private airstrip is located at the Iliamna Roadhouse, and Summit Lake provides private float plane access. A paved road connects Iliamna to the Iliamna airport, as well as the community of Newhalen located several miles to the south. During the winter, a road is passable between Iliamna and Nondalton, 15 miles to the north, although the road is only paved half way. Construction of a bridge is proposed at the western end of Six Mile Lake, which would provide year-round access to Nondalton. In addition, an unimproved trail, the Williamsport-Pile Bay Trail, runs along the northern shore of Iliamna Lake, connecting Iliamna and Newhalen with the communities of Pedro Bay and Pile Bay Village to the east. Pile Bay Village is also connected to Cook Inlet by road. This corridor is used to transport fishing boats and supplies between Cook Inlet and Bristol Bay, but is considered difficult to use.